Brake operator



6 Sheets-Sheet 1 awk Q E u n.

April 3, 1945. B. H. MOSSINGHOFF BRAKE OPERATOR Filed Aug. 16, 1941 6Sheets-Sheet 2 April 3, 1945. B. H. MosslNGHoFF BRAKE OPERATOR FiledAug. 1e, 1941 April 3, 1945. B. H. MosslNGl-IOFF v2,372,842

BRAKE OPERATOR Filed Aug. 16, 1941 6 Sheets-Shet 3 April 3, 1945. B. H.MosslNGHol-'F BRAKE OPERATOR Filed Aug. 16, 1941 6 Sheets-Sheet 4 April3, 1945. B. H. MosslNGHoFF BRAKE OPERATOR Filed Aug. 16, 1941 6Sheets-Sheet 5 April 3, 1945. B. H, MosslNGHoFF 2,372,842

BRAKE OPERATOR Filed Aug. 16, 1941 6 Sheets-Sheet 6 Inventor W PatentedApr. 3, 1945 UNITED STATES. PATENT oFFlcr-z BRAKE OPERATOR Bernard H.Mossinghofl', Chicago, Ill.

Application August 16, 1941, Serial No. 407,115 2o claims. (ci. iss-iro)stroked brake pedal with its' work stroke em- 'l'his invention pertainsto brake operators, with particular application to the wheels of motorvehicles. Reference is made to my application Serial No. 399,908, ledJune 26, 1941, presenting and claiming accelerator disconnectors,including the type herein disclosed. Also, to my application Serial No.253,485, led Jan. 30, 1939, which issued into patent numbered2,311,120'disclosing and claiming a. brake operator of the generalpurposes as the herein. Also, to my application, Serial No. 404,688,filed July 30, 1941, presenting a low-pedalled directly powered form ofbrake operator.

The aforesaid applications present the chief objects generally,particularly that of safety through accident prevention, by a quickerthan customary application of the vehicles brakes. It seems establishedthat with the present common brake pedals and system, about 3A of asecond is required, with quickest emergency effort,

before the brakes begin to pressure apply. This corresponds to 66 feetof un-braked car roll, at 60 M. P. H. This invention aims tosubstantially reduce such time and road distance requirement, byproviding a low-positioned pedal, preferably of about the heighth of theconventional accelerator pedal; and moreover, preferably an arrangementpermitting the foot to quickly slip-over by slight lateral rock on heelfrom its accelerating position to its position over the brake pedal. Tobetter accommodate this purpose, I provide, in combination, that theaccelerator pedal become automatically disconnected or made ineffectivefor normal engine control upon the initial operation of the brake pedal,thus permitting a substantial portion of the foot to remain over theaccelerator pedal While operating the preferably lightly resistant brakepedal. Such objects, as drivers convenience, etc., as outlined in myaforesaid co-pending applications, are also served.

It is aimed to adapt the use of the low-cost and simple vacuum-poweredsystem for such lowand quickly-operable brake pedal feature. In view ofthe occurrences of vacuum failure, such adaptation would presentproblems, which my novel provisions solve. The present disclosureinvolves the use of a strongly tensioned spring to apply the brakes,with vacuum power releasing the brakes and reenergizing the spring. Itpresents the novel feature that, should the vacuum fail to release thebrakes, an automatic overnormal retraction of the brake pedal to aconventional-like long-stroked position would release the brakes, withsubsequent braking being permitted muscularly through suchconventional-like longciency. Thus, I remove the serious defect ofindirectly powered system (spring-applied) to insure brake release, arequirement for accidentprevention, while providing the advantage of theindirectly-powered system in assuring brake application by a compressionspring, laterally contained so that a break in the spring would notrender it ineffective. Such provisions are presented in my application253,485; the application 404,688 disclosing a. directly vacuum poweredsystem.

Particularly in the heavier type of vehicles, a brake pedal leveragedfor suitable lightness, and connected for itself muscularly to operatethe brakes upon power failure or to supplement delicient power, mighttend to retract an impractical amount to its long-stroked brakereleasing position upon failure` of the power to release the brakes, ifspecial provision is not made therefor. In the aforesaid application253,485, a bell-crank form of leverage changer is disclosed. In thispresent application I feature another form of leverage-changer,apparently better adapted for a larger leverage ratio changeparticularly for the heavier type of vehicles. I furthermore providenovel lock means, whereby predominance of foot pressure over that of thepower actuator will not push back the power actuator in a dierentallyconnected system, thus permitting the foot muscularly to supplement thepower upon its accidental or designed deficiency. Such lock means isfurthermore presented as adaptable for a unitary assembly with the powermotor. Moreover, I disclose a novel pressure-indicated or socalledcompensating principle of valving for an indirect vacuum powered system.Further objects will become apparent from the disclosure and asdescribed.

In the illustrations:

Fig. 1 presents a side elevational view, partly in section, of my deviceas connected for operation of the conventional master cylinder ofhydraulic brakes.

Fig. 2 shows a lateral elevation of the accelerator disconnecting deviceof Fig. 1.

Fig. 3 presents a lateral elevation of an enlarged detail portion ofFig. 1.

Fig. 4 is a sectional detail view, taken along line 4--14 of Fig. 3.

Fig. 5 presents a sectional detail view, taken along line 5 5 of Fig. 3.

Fig. 6 presents a side elevation of the leverage changer portion in theposition with the brake pedal fully retracted to its abnormallong-stroked position, with the brakes fully released.

Fig. 7 presents the leverage changer portion of Fig. 6 in the positionof purely muscular application of the brakes, the power having.previously failed.

Fig. 8 presents a laterally sectional view of details of parts withinthe tube 50 unitary with the vacuum motor of Fig. 1. It shows theunidirectional lock mechanism.

Fig. 9 presents a transverse section, taken along line 3--9 of Fig. 8.

Fig. l presents sectionally a detail modification for a portion of thedevice shown in Fig. 8.

Fig. 11 presents laterally sectionally a modication to supplant thedevice shown in Fig. 8, incorporating also in the unitary assembly theactuating spring 69 (Fig. 1).

Fig. 12 presents mostly sectionally a modification for a portion of Fig.8.

Fig. 13 presents a lateral elevation, partly in section, of amodification in the form of another lock principle to supplantsubstantially the whole device of Fig. 8.

Fig. 14 presents in lateral elevation a modification of the leveragechanging system to supplant the disclosure of such portion in Fig. 1 andin Figs. 3 to 'l inclusive.

Fig. 15 presents side elevationally and partly sectionally amodification in the form of a compensating type valve to replace thevalve 42 of Fig. 1 and the cushion spring 16 shown in Fig. 4. The viewis along the line |5-I5 of Fig. 16.

Fig. 16 is a transverse mostly sectional view, taken generally along theline |6-I6 of Fig. 15. It discloses in detail the fairly leak-proofcheckvalve portion, in combination with the control valve.

Fig, 17 presents in elevation a composite unit of the inventioninclusive of the modifications of Figs. 13 and 15.

The device of Figs. 1 to 9 The brake pedal I5 is rockably mounted on thexed bearing pin I6 and has an arcuated arm passing through the footboard I1 terminating in the foot pad I8 as an integral part of thepedal. On the same foot board is pivotally mounted the conventional-likeaccelerator pedal I9, a torsion spring 20 however encompassing thepedals fulcrum pin so as to tend constantly to hold the pedal in itsrearmost position shown in Fig. 1, and which accelerator pedal throughits thrust rod 2| connects pivotally with the lever 22 rockably mountedon the cross shaft 23, which is itself rockably mounted in the bracket24 affixed onto the foot boad I1. To this cross shaft is afiixed thelever having an arm 25 carrying pivotally the pawl lever 26 normallyregistering with some lost-motion provision at 21 with a detent in theperiphery of the lever 22. To the pawl 26 is laterally xedly riveted thearm 28 carrying pivotally at its end the operating pull rod 29 leadingto the floating lever to be later explained, so that a downward pull onthe said rod would remove the pawl 26 from its engagement with the lever22 against the tension of the tensioned tensile spring 30 constantlyurging pawl engagement. Another arm 3| integral with the arm 25 carriesthe connecting link 32 pivotally connecting with the moving extremity ofthe lever arm 33 aflixed for co-movement with the throttle valve 34 forthe engine intake manifold '35 of the vehicles engine 36, the tensilespring 31 tending constantly to hold the lever 33 against the stop 38urging the throttle closed, as conventionally, an idler adjustment screwbeing providable as conventionally. Said throttle and connections aremerely representative, since acceleration control for a Diesel engine orelectric motor require different constructions. 1

'Ihe tube 40, connecting into the engine's intake manifold 35, leadsthrough a conventional shut-off cock 4| to the combined controlandcheck-valve 42, full details of which valve are understandable from Fig.2 in Pat, No, 2,311,120 though it may otherwise be of any suitablestructure, for controllably connecting the vacuum motor 43 of thewell-known rubber diaphragm type, either with the atmosphere oralternatively with the manifold 35 as the vacuum source. The check-valveelement of\ the valve 42, as detailed in the aforesaid patent and alsoin Fig, 16 herein affords a fairly leak-proof construction. 'I'hecontrol valve portion of the valve 42 has a neutral position wherebyconnection both to the atmosphere and to the intake manifold 35 issimultaneously closed. A tensioned spring inside of the valve 42 tendsconstantly to urge the grit-capped stem 44 upwards against the valvecontrol lever 45 to reestablish communication between the vacuum motorand the manifold 35 upon brake release.

The vacuum motor 43 is of the conventionallike rubber diaphragmed type,comprising the diaphragm rubber 41 held as conventionally between twometal plates clamped together by the threaded nut 48 screwed onto theshouldered stem 49 leading rearwards (rightward viewing the drawingFig. 1) to a connecting mechanism 1n the tube 50 afiixed unitarily tothe vacuum motor 43, for purposes to be later described. The nut 48abuts against a rubber cushion 52 axed to the inner wall of the vacuummotor. A conical compression spring 53 tends constantly to urge thediaphragm and stem 49 rightwards against the vacuum suction existingnormally in the chamber 54 when the brakes are in release as shown inFig. l, with the chamber 54 being in communication with the enginemanifold 35.

Referring now to Figs. 1, 3, 4 and 5: Pivotally mounted on the fixedbearing pin I6 and to both sides of the brake pedal's bearing boss isthe stamped substantially channel-shaped radius and supporting lever 51,carrying by means of the pin 58 the floating lever 59, connecting at pin60 with the plunger rod 6| of the conventional master cylinder 62 withits standard liquid reservoir 63, as mounted on the xed plate 64, of theconventional hydraulic brake systems. Rightward movement of the plungerrod 6| applies the vehicles brakes. At the lowest extremity of the saidfloating lever is connected by means of the pin 65 the connecting rod 66slidable through the bushing 61 ailixed to the cylindrical enclosuretube 68 containing the strongly tensioned com-pression spring 69 bearingagainst said bushing 61 and the plate 10 aflxed to the extremity of therod 66. The tube 68 is pivoted at the fixed point 1| onto the vehiclechassis. It is characteristic of such laterally conned compressionsprings that, should the spring break, it would remain substantiallyeective. The actuating spring 69, accordingly, constantly tends to forcethe pin 65 and therefore the floating lever to the right for brakeapplication, and becomes so operable upon release of the resistantvacuum suction in the chamber 54 of the motor 43.

The upper end of the floating lever 59 is bifurcated (Figs. 9 to 5).thus permitting e suitably oiset lower arm 19 of the brake pedal Il tobe accommodated between the prongs of the fork' assembly and to providesome preferable initial tension for the spring. The left end of thespring barrel member 19 carries the pin 9| and is forked to accommodatean end of the short thrust link 92 pivoted on said pin, the left end ofwhich link is open-slotted at 99 to encompass the diametrically reducedportion of the headed stud I4 firmly aillxed in the pedals lower arm 19.Similarly affixed in said arm is the check stud 95 to serve as upperlimiting stop for the link 92, said stud having a shallow groovepreferably of inclined walls to receive and retain for better alignmentthe link 92.

Pivotally carried by the aforesaid pin 9| is the upper forked end oi therod 96, the prongs of which are to both sides of the link 92, and whichrod has a shoulder l1 bearing against the initially tensionedcompression spring 89, the lower end of which spring bears against thespherically concaved bushing 89 slldable over the rod 99, the bushingcooperating with a correspondingly spherically convexed nodule formed inthe ilxed plate 90, the slot 9| permitting swinging freedom for the rod96. Screwed onto the lower end of the rod is the ball joint nut 92,adjustable by the lock-nut 93. 'I'he plate 90 serves also as a stop forthe floating lever 59. It is obvious that the described structurebetween the pins 14 and 94 constitute a double-linked toggle, with acushion spring therebetween, which toggle will |be collapsed upon thepin 9| moving downward relatively to the pedal arm 13, in other wordswhen the stud 94 moving with the clockwise rocking of the pedal on itsfulcrum pin i9, is raised upwards to the position shown in Fig. 6,Awhich is that of an abnormally retracted brake pedal to its long-strokedposition. In Figs. 1 and 3 the toggle is securely locked, due partly tothe position of the pin 9| being above the line drawn from the stud 84to the pin 14, and due further to the tension in the spring 99.

For valve operation, the right end of the connecting rod 95 is pivotallyconnected at 96 with the floating lever 59 in any suitable manner asthat of a 90 degree bend of the rod end, which rod slides through thebushinged end of the spring enclosure tube 91, thence passes through thetensioned compression spring 98 and has the collar 99 afllxed at its endagainst which said spring bears to urge the rod 95 leftwards relative tothe cylindrical tube 91. Said collar 99 abuts against the bushing |00aflixed to the tube 91, into which bushing is threaded and locknutted bymeans of the nut |0| the rod extension 96 connecting at its left endpivotally with the valve lever 45. The initial tensioning in the spring98 is suilicient to assure that the rods 95 and 96 move in unison asthough one piece for the normal operation of the valve 42, lbut thespring will permit the foot pad I 9 of the brake pedal to move fully tothe foot board |1, though the movement of the valve stem 44 be limited.

I will now describe the non-reverse locking device which is enclosed inthe tube 50 and is shown in detail in Figs. 8 and 9. The diaphragm rod49 of the vacuum motor 4I (Fig. l) has integrally or suitably afllxed toits right end the cylindrical member |03 having the continuously annulargroove |04 and the cylindrical head portion |05. In said groove |04 areloosely inserted the ilanged ends of the three identical friction shoes|09, |09' and |09" (Fig. 9) mutually closely fltting to form virtually aperipherially complete enclosing cylinder, the right ends of which threefriction shoes being similarly flanged to radially project in thecontinuously annular groove |01 formed in the cylindrical piston member|09, having an enlarged cylindrical plunger head portion |09, and havingits right end bored to suitably accommodate in the manner oi a ballthrust joint the partially spherical head ||0 integral with theconnecting rod threaded into the clevis I2, whichpivotally connects withthe pin 65 of the floating lever 59 (Fig. 1), to which clevis the rod isheld by the adjusting nut ||3. The head portion ||0 is retained inball-joint manner in the member by means of the retaining bushing ||4itself held in place by the soft metal expansion ring H5. It is apparentthat the described parts serve to transmit the suction pull of thevacuum motor's diaphragm 41 to the floating lever 59 for swinging andholding it in its shown leftmost position against the strong tension ofthe actuating spring 69 (Fig. 1).

The solid and cylindrical rubber bar ||9 is placed within thecylindrical hollow formed by the said friction shoes, as |06, andbetween the two plunger heads |05 and |09, with suilicient loose llt toallow for thermal expansion of rubber. 'Ihis solid rubber bar haspreferably a soft rubber core to provide Ibetter pressure dispersingfluidity, the outer shell of the rubber being preferably of hardervulcanized durometer characteristics. Accordingly for its fabrication,the rubber bar ||5 may optionally be of two parts. The right end of therubber bar is preferably somewhat convexed to provide surplus initialexpansion space. The whole so far described as internal to the tube 50form a unitary assembly axially slidable in the enclosure tube 50, whichis shown as of a casting, and lined with preferably a non-squeak softmetal liner ||1, of soft brass or of lead with sufficient antirnony toresist fluidity under pressure, or of any suitable material. Theconventional-like longitudinally expansibie rubber dust guard I8,mounted between the rod and the tube 50, closes the right end of saidtube. The mounting ears as 5| (Fig. 1) serve to hold the entire motorand lock tube assembly fixed on the vehicle chassis, the motor 43 beingafixed in any suitable manner onto the tube 50, such as :by means of thecircular reinforcing plates ||9 and |20, the part |2| being a cup-shapedgrit cver over the conventional perforations of the vacuum motor toatmosphere.

As to the operation of the parts in Figs. 1 to 9, so far described: Thepositions shown in full lines in Fig. 1 are that of the brakes fullyreleased, and with the vacuum having been properly available andoperative to give the shown low position of the brake pedals foot padi8, which is its normal position, with the foot of! of the pedal.

Assumedly. the driver has. in the previous inetant. removed footpressure from the accelerator pedal preparatory to quick brake'application. For this purpose his foot is preferably retained restingon its heel, rocking the foot laterally on the heel to top atleast aportion of the brake foot pad Il, thus saving the time required forbodily relocating his foot even on a low-positioned brake pedal. 'Iheinitial depression of the brake pedal il causes the pin 14 to move tothe right, thus causing a rightward pull on the valve rods IB and Il toforce the valve stem 44 downwards, with the effect of first closing thecommunication between the chamber I4 and the intake manifold It, andinstantly thereafter opening communication between the said chamber I4and the atmosphere. The valve and its connections arc arranged so as .zorequire only a small amount of movement of the valve stem 44, or of therod 4B to enect such valve operation. The consequent admission ofatmospheric air into the chamber i4, permits the actuating spring 84 toswing the floating lever Il counter-clockwise on the pin 14 as thefulcrum, to apply the brakes by forcing the master cylinder plunger 4Ito the right. Upon the initial swinging of the noating lever 5I, a pullis exerted downwards on the accelerator disconnector rod 29, to removethe pawl 2l from the peripheral path of the lever 22, thus permittingthe foot to remain even mostly over the accelerator pedal i9 whilebraking. since its depression would revolve the lever 22 freely on theshaft 23 without eil'ect on the lever arm Il and on the throttle I4.Lost-motion at the pawl engaging point 21, or optionally alternatively asurplus heighth of the brake pad i8 over the foot surface of theaccelerator pedal l! (both provisions are shown in the drawings) wouldprevent frictional contact with its consequent wear of the functionalpawl surface during the prompt operation. Further details and forms ofaccelerator disconnectors, adaptable to the herein disclosed, arepresented in my application 399,908 aforementioned, some forms providingthat the accelerator pedal become virtually the brake pedal upon similarfoot movement.

The cushion spring 18 (Fig. 4) is preferably initially tensioned to anextent at least so that the parts and 18 move as one piece during theaforesaid initial valve operation. However, the

yreaction force from the master cylinder plunger Il causes leitwardpressure on the pin 14, which will to a corresponding degree compressthe cushion spring 16, which spring compression has the tendency to movethe valve rod leftwards to check the vacuum exhaust from the motor 43 (Ispeak oi' vacuum as though it were positive pressure), with the resultthat the force on the master cylinder plunger 6| registers with theamount of compression of the cushion spring 16, which itself isdetermined by the foot pressure on the brake pedal. The said cushionspring 16 is strong and functionally short having a high amount oftension variation per compression stroke. Optionally, it may be designedto function throughout the total of normal pressure braking, or it maybe made to compress functionally for only the lower range of brakingpressure, before the shoulder 19 abuts against its stop to check thesprings compression. This spring 16 accordingly serves the purposes ofvalving modulation, also to prevent shock to the braking system, andincidentally to obviate the illusory feeling, gained from experience, ofthe foot pad I8 travelling to the right during braking pressureprogress. How- Gil asmssa ever, the optional location of the pivot pointil (Fig. 5) of the valve rod higher than instead d on the pivot pin 14aids to serve the lult indicated Purposes. so that the cushion spring 14may even optionally be dispensed with, in which case the parte 1I and 1lwould be constructed as one piece. Due to the shown location of thepoint Il, the counter-clockwise swinging of the floating lever Il uponbrake application as described, and on the pin 14 as its fulcrum, wouldnecessitate a gradually further depression of the brake pedal pad I4with the gradual swing of the lever II, in order to maintain the valvelever 4l in a virtually constant position of valve opera tion, lust atthe verge of exhausting more vacuum from the chamber I4 for higherpressure braking. the movement of the valve rod il being designed to beshort for the valving control. My application 253,485 of previousmention discloses further details of the valving control. It should benoted that the floating lever Il is differentially connected for thepivot points 14, It and IB. 'I'he hydraulic braking pressure isdetermined by the foot pressure on the brake pedal. Moreover. the shownmutally reactive differential interconnection in volves a virtual racebetween the foot and the power actuation. The power unit and actuatingspring 4l is therefore preferably made strong, optionally sufilcient totake care of the maior part if not all of the normal pressure braking,particularly in view of the resistance oered by the flow of hydraulicliquid through its circuitous passages and restrictions during quickbrake application. This would not apply to the same degree to so-called"mechanical" brakes, for the actuation of which the herein disclosedinvention is likewise adapted, by the use of a thrust rod connection tothe pin 60, similar as disclosed in my application 404,688.

As to the operation of the non-reverse lock device of Figs. 8 and 9: Itoccurs with vehicles that abnormally high braking pressures are at timesrequired, for which it seems preferable not to provide an actuatingspring and vacuum power capacity to meet. Moreover, it is optional toprovide a power capacity insufficient to take care even of all normalhigh pressure braking. Joined with these considerations, it mightfrequently occur that the brake pedal, when operative to muscularlysupplement the deficient power, would creep too near to the foot-boardi1, especially in heavier vehicles relative to the leveraging for thelight pedal pressure requirement, for which situation it would be usefulto retract the pedal for a moment for the sake of pedal recovery to ahigher position from the foot. board for subsequent further brakingmuscularly. For such-like reasons I provide the unidirectional lockingdevice of Figs. s and 9. After the limited capacity of the power systemincluding that of the actuating spring 69 (Fig. l) has moved thefloating levers pin 65 to the right as far as its force capacitypermits, further supplemental foot pressure cn the brake pedal will tendto move the said pin 65 leftwards. However, such supplemental pedalpressure and consequent psrtial further depression of the pedal willhave pulled the valve rod still further rightward with the result offull breakdown of all vacuum in the chamber 54 of the vacuum motor,thereby permitting the conical spring 53 of the vacuum motor to push thecylindrical member |23 and its associated friction shoes as |06rightwards, with the piston head |09 associated with the brake pedalmovement remaining stationary or tending to move leftwards in the tube58. As a consequence the rubber bar ||8 will be axially compressed, forwhich function the aforesaid conical spring 53 is to be of suilicienttension. Rubber being practically incompressible volumetrically, andhaving fluidity characteristics, the rubber bar IIB will expandlaterally to press the friction shoes, as |06 against the friction liner||1 of the tube' 5|! for initial frictional grip to prevent easy axialsliding of the assembly internal to the tube 50. The tension of theconical spring 53 is securely suilcient to accomplish such initialfrictional grip. Upon further pressure and depression of the brakepedal, the plunger head |09 will press still further on the rubber bar||6 t0 increase the frictional bind between the shoes as |06 and theliner |I1. The quantitative design of the exposed lateral area of therubber bar ||6 in ratio to its cylindrical diameter are such thatautomatic self-locking is obtained with a margin to spare, so that theheavier the leftward pressure on the rod the more the frictional bind,and in greater relative proportion. A thicker portion of the rightconvex end of the rubber bar H6 is preferably made of harder rubber forgreater security of pressure distribution through the body of the rubberinstead of the peripheral edge of the metal plunger head |09 coming intoabutment with the rubber. The inner edges of the metal friction shoes as|06 (though they may be of other materials than metal) at their mutualjunctures are somewhat rounded to prevent pinching of rubber at suchjunctures upon pressure release. It is apparent that should the driverlet the brake pedal back from a position close to the vehicles footboard |1, a position as might have been due to the thermal expansion ofthe vehicles brake drums which demands compensatingly a longer pedaldepression, or due to hydraulic liquid leaks from the brake system, etc.during the current braking operation, the actuating spring 69 (Fig. 1)will move the assembly internal to the tube 50 still farther rightwardduring such pedal retraction, with the result that the lock device ofFig. 8 will assume a more rightward position in the tube 50, withconsequent new and more retracted position of the brake pedal forfurther braking. It is obvious that a material of suitably highfrictional coeicient may replace the liner H1, or the surface on theshoes |06.

As to the retraction of the brake pedal to its abnormal andlonger-stroked position: This is perhaps better understandable bydescribing the fuller retraction of the pedal upon a vacuum leak fromthe chamber 54 presumablythrough the valve, as when the vehicle standsinoperable in the garage. Such gradual vacuum leak would permit theactuating spring 69 (Fig. 1) to gradually force the pin 65 rightward.Since I preferably provide lost-motion as shown between the spring lug|23 integral with the lever 59 and the enlarged end |25 of the closedcoil but initially tensioned tensile retract spring |24 (Fig. l), theinitial swing rightward of the said pin 65 will push to the right themaster cylinder plunger 6|, to first take up the customary lost-motionof such plungers, and thereupon to move the master cylinder pistonslightly until the customary compen sation drilling, a very smalldrilling in conventional hydraulic brake master cylinders, is covered bythe lip of the master cylinders rubber cup. At that point the hydraulicresistance is that caused by the brake shoe retract springs. If suchshoe retract springs are designedly not of suf- Cil tlcient resistanceto cause the brake pedal I5 to start its retraction movement to itslong-stroked position, indicated by |5a (Fig. 1)-, the disclosedlost-motion between the lug |23 and the retract spring end |25 must"first be taken up by a, corresponding counter-clockwise swinging of thelever 59, so that contact between the said lug |23 and the spring end|25 will add suillcient resistance to cause the possibly cumbersomebrake pedal I5 to rock on its bearing Din I6 clockwise by reason of theleftward thrust through the member 18 (Fig. 3) due to the leftwardpressure exerted on the pin 14 by the aforesaid counterclockwiseswinging of the lever 59. Particularly after contact of the lug |23 withthe spring end |25, the gradual rightward swinging of the lever .59 willaccordingly cause the brake pedal I5 to gradually approach itslong-stroked position |5a, instead of forcing the master cylinderplunger 5| to move to the right causing .brake application. Moreover,after contact of the said lug |23 with the spring end |25, the lever 59will reassume its shown contact with the check plate 90, thus, assuringuncovering of the master cylinders compensation drilling aboveindicated.

However, because of the leverage inherent in a system which provides asuitably light pressured brake pedal especially in a heavier vehicle forthe normal low-pedal braking operation, the 'brake pedal |-5wouldretract an impractical amount by the time that the pin 65 reachesits rightmost limit as actuated by the spring 69 and as determined inthe disclosed structure by the limiting contact of the end of the rod 56against theright wall of the spring tube 68. `For which reason I providea leverage changing mechanism, operable during the said abnormalretraction of the brake pedal and serving to reduce the amount ofretraction stroke of the pedal so as to position the pedal a practicaldistance from the foot board I1 for its abnormal longstroked condition.However, since the occurrences for the long stroked muscular braking assubstitute for the failing power, are highly infrequent, the brake pedalmay satisfactorily assume a more rearward position than customary, sincenormal convenience/is not a consideration, as it is conventionally.During the afore-described retraction movement of the brake pedal |5,the pin 8| describes a leftward moving arc with the ball joint at 92(Fig. 3) as a center. As is apparent from Fig. 6, this has the effect ofcollapsing the toggle comprising the member 18,

so that the lower arm 13 of the brake pedal con- 1 tacts the pin 58,which contact would remain effective for subsequent muscular operationof braking, as substitute for the power, during which muscular brakingthe spring 88 would compress as disclosed in Fig. '1, a view of footpressure applied braking.

The pedals lower arm 13 in relation to the pin 58 has moreoverpreferably another. DUIPOse. For the normal low-pedal powered braking,it is preferable to quantitatively design the lever system, so that thesaid lower pedal arm 13 contacts the pin 58, and thus transfers theleverage from the pin 14 to that of the pin 58 before the pedal pad |8would otherwise reach fully to the floor board 1, when supplementing thepower as previously described, and so operable even under the conditionof the brake shoe linings having worn so as to cause the actuatingspring B9 to have reached the limit of its stroke, indicated by thedotted outlined position 55h (Fig.

1) for the position of the lever 59. This however is optional. Suchleverage changing before reaching the foot boards would have the purposeof 'checking the rate of depression of the pedal in its furtherdepression movement, with correspondingly heavier foot pressureinherently involved in the leverage change. It becomes apparent,incidentlly, thatshould the brake shoe linings be worn beyond the strokecapacity of the actuating spring 69, the brake pedal I would depress anoveramount for further braking, though the vacuum be available, whichoverdepression of the pedal may be taken as an indication by the driverthat the shoe linings are to be newly adjusted. However,in a heavyvehicle, particularly of the commercial class, it seems preferable toprovide an electric bulb indicator for such adjustment requirement asis` disclosed in my application 404,688. On basis of quantitative designwhich provides that the arm I3 contacts the pin 58 before the pedal padI8 reaches the foot board I1 during normal operation, but whenmuscularly supplementing the power, and even when the brake linings areworn beyond the capacity oi.' ,stroke of the actuating spring 69, asabove indicated, it would imply that the toggle comprising the member I8would virtually straighten out for the view of Fig. '1, when the brakelinings are so completely worn with consequent further depressionposition of the brake pedal than is shown in Fig. 7.

When the previously wanting vacuum suddenly becomes available, as whenrestarting the engine after a long period in the garage, the vacuummotor would pull the pin 65 to the left thus swinging the lever 58clockwise while resting on the stop 9U as a fulcrum, therebystraightening out and setting the toggle (view Fig. 6) to return thelever system to the position shown in Fig. 1, ready for the normallow-positioned pedal and powered braking operation. As to the dottedoutlined positionsof the brake pedal pad I8, disclosed in Fig. 1, theposition I8a is that of operation of the valve 42. The position I8b,which is designedly optional and dependent on the functional tensionvariation of the chosen cushion spring 16 (Fig. 4) (assuming that thepoint 96 (Fig. 3) coincides with the pin 14), is that of the brakesfully pressure applied for normal braking by the power system; anabnormally high braking pressure operation in which the foot muscularlysupplements the power would fetch the pedal somewhat lower than thatindicated by I8b. The position I8c is that of the lower arm 'I3 of thebrake pedal contacting the pin 58 upon muscularly supplementing thepower and when a long stroke is demanded due to lining wear or perhapsdue to overhcated and thermally expanding brake drums. The position I8dindicates the farthest depressed condition of the brake pedals pad, whenthe foot muscularly supplements the power with largest permissible brakeshoe lining wear. When the foot pad moves from the position Isc to thatof I8d, the link 82 (Figs. 3 and 4) would move to the right relative tothe stud 84, the open slot at 83 permitting such surplus pedaldepression. It can be quantitatively arranged that should the poweroperate satisfactorily for a, long period of time, so that the brakeshoe linings become worn to the capacity of the stroke of the actuatingspring 69, and that should thereafter the vacuum suddenly failnecessitating the long stroked pedal operation indicated by Figs. 6 and7, the pedal would remain effective for such muscular operation' beforethe pad I8 reaches the foot board I1. However, this is optional,particularly since lining wear conditions can be inspected in advance,otherwise.

Although the abnormal long pedal stroke operation has Just beendescribed on the basis of s vacuum leak from the chamber I4, it shouldbe apparent that the brake pedal retraction to its long stroked positionwould occur when the vacuum motor fails to release the brakes, the saidlong stroked retraction of the pedal releasing the brakes as asubstitute for the power. This is useful for accident prevention.Furthermore, if there be a leaking tendency from the chamber 54, theleak would actually become effective while driving with the throttlewide open. particularly when the vehicles engine is under heavy load andnot speeding, because of vacuum pressure reduction at the source. Undersuch condition. if provision were not made for'the pedals abnormallylong retraction, the brakes would become applied instead, thusindicating another useful purpose of the provision. However, should thebrake pedal have assumed its long-stroked position while driving withfull throttle and under conditions of s. leak as just above assumed, thebrake pedal would instantly return to its normal low-position shown inFig. 1. upon release of the accelerator pedal, due to the suddenlygreatly increased vacuum pressure upon such throttle closing,particularly with a speeding engine. An added provision of a vacuumreservoir tank with a leakless checkvalve type of Fig. 16, as isdisclosed and described in my application 404,688 would almostcompletely compensate for such assumed leak. Incidentally, my softrubber seated valve structure disclosed in my application 253,485 hasbeen proven in practice to be fairly leak-proof for long periods. Itwill be observed that a downward pull is exerted on the acceleratordisconnector rod 29 (Fig. l) thus effectively disconnecting theaccelerator, when a leak from the chamber 54 permits the pin 65 to moveto the right. This would be an indication to the driver while attemptingto accelerate, that the brake pedal is assuming its abnormallong-stroked position. Ii' the accelerator disconnection occurs whileholding the accelerator pedal I9 depressed, the sudden closing of theengine throttle 34 would immediately replenish the vacuum in the chamber54, and in the vacuum reservoir tank, if such be employed, whereuponafter letting back the accelerator pedal momentarily, acceleration canproceed. However, accelerator disconnectors are disclosed in myapplication 399,908, which are operable for accelerator disconnectiononly while intentionally braking, if the above intimated indication tothe driver be not desired. One of such disclosed forms provides that therod 2,9 co-moves with the pin after some lost-motion.

As to the normal brake release operation when the normal low-positionedbrake pedal and the power system is effective: Release of the footpressure from the pedal pad I8 permitting the brake pedal to retract,due to the hydraulic reaction pressure in the brake system, to the brakeshoe retract springs, to the retract spring I24 and to the springtension in the valve 42, the valve 42 would become operable to establishcommunication between the intake manifold 35 and the chamber 54l thusintroducing vacuum suction in the chamber 54 causing the vacuum motor 43to pull the pin 85 leftwards against the tension of .the actuatingspring 68, to return all of the parts to the brakes released positionshown er motor and of the lever 59.

in Fig'. l. It is meant in the disclosure that the tension oi a springin the valve 42 urging the valve stem 44 upwards to its limit shown, issufficient to return securely the pin 14 leftwards to its position shownin Fig. l, notwithstanding an upward tl^rust through the lever 59, dueto the non-parallellism of the power rods and 66, and in view of thenon-alignnent linearly of the pins 66, 68 and I6. However, if the depthof the vehicles chassis suitably permits, it is preferable to mount theswivel point 1I of the actuating spring tube to a lower position, oralternatively to lower the vacuum motor 43, so as to substantially alignthe rods and 66 to reduce or cancel the sine factor; or by theapplication of other provisions well-known to engineers. It should benoted that the initial tension of the spring 98 (Fig. 1) in the valverod connection dominates over the tension of the valve spring in thevalve 42. The position of the brake pedal pad I9 is determined, at leastprimarily by the adjustment of the ball joint 92 (Figs. l and 3), thestored tension in the compression spring 68 being sufficient to securelysupport the weight of the brake pedal.

.Now as to the purpose of the lost-motion shown between the lug |23 andthe spring end |25 (Fig. l): When the drivers foot is released from thefoot Dad I6 with fair quickness for brake release,

the vacuum motor 43 might not act as promptly to reach the full brakesreleased position shown. particularly since the cushion spring 16 (Fig.4) functions to make the system a pressure-Indicated one, whereby thetension of the said cushion spring in moment must be reduced throughfoot pressure release below the tension moment of the brake shoe retractsprings before the vacnum motor (due to valving control) would negotiatethe longer retract stroke which advances the brake shoes away from theirdrums. Moreover, the initial tension of the said cushion spring 16 mightoptionally be made to predominate over the said shoe retract springs. Ifthe retract spring |24 for the lever 59 were connected as conventionallywithout lost-motion between |23 and |25, the brake pedal upon footrelease therefrom would continue to retract a surplus amount be` yondthe position of the foot pad I8 shown in Fig. l, momentarily until thevacuum motor would catch up and cause the lever 59 to rest on its stopplate 90 I Fig. l), This might occur though the action of the vacuummotor be designed very prompt. The lost-motion between the lug |23 and|25 would make the retract spring |24 inoperative to retract the brakepedal during the nal portion of the retract movement of the pow- Saidlost motion may be made of sufficient amplitude so as to securely havethe effect merely to cause contact between the lever 59 with its reststop on the plate 90, when the pin 65 has travelled rightward, as may bedue to vacuum leak from the chamber 54. to its dotted outlined position65h indicating the capacity limit of the power stroke system. This, inthe matter of degree, is optional; as is furthermore optional theprovision of an additional spring such as spring 94 (Fig. l), to aid inretraction of the lever 59 with a tension insufficient to causeretraction of the pedal pad I8 beyond its shown position in Fig. 1. Suchadditionally provided retract spring obviously would assist the springin the valve 42, which latter as a consequence would be constructed oflighter tension. Such are matters mainly of mechanical ingenuity, andgive consideration to the cumbersomeness of the pedal lever system ofthe particular design or vehicle. However, the precedlnghas beenpresented for ease of understanding, since the supposition assumed doesnot fully hold true on basis of the disclosure. The location of thepivot point 96 (Fig. 3) of the valve operating rod 95 has the effectthat the brake pedal must be retracted for normal brake release asurplus amount beyond that indicated by the remaining tension in thecushion spring 16', therefore it provides more time for the brakerelease operation of the vacuum motor 43. Whereas the cushion spring 16employs the pressure-indicated principle, the location of the pivot`point 96 higher than the pin '|4 employs the movement-indicatedprinciple, the disclosure showing a compromise of the two, and as aboveintimated either principle may optionally be employed solely, therebyaffecting the problem of a surplus bounce-back of the brake pedal pad I8upon brake release. Involved in this problem is the fact that thepositions of the valve stem 44 for brake application and for brakerelease are notrfully coincident, though the intervening movement of thevalve stem be designed as small as practical.

When the brake ypedal I5 is fully retracted t0 its abnormal long-strokedposition, as is shown in Fig. 6, the master cylinder plunger 6| is fullyretracted with the lever 59 resting on its stop 9|). However such fullretraction is not as importantly required for mechanical brakes, since aretraction of the brake shoes away from their drums to about half of thenormal retraction distance might be considered satisfactory for thehighly infrequent long-stroked muscular application of the brakes. Thismatter quantitatively affects the leverage design and the matter ofamount of retraction of the pedal. So also such full retraction of themaster cylinder plunger 6| is not sol irnportantly required with theearlier types of hydraulic brake master` cylinders employed onautomobiles, before the pumping feature has been introduced (brakeliquid replenishment by speedy reciprocation of the pedal). It should benoted however that, when the currently conventional pumping type ofmaster cylinder be used, more eective pumping is attained by mydisclosed invention, due to the speed of reciprocation o! the disclosedpower system by valving with the short stroked pedal, as compared withtodays conventional brakes. The full retraction position shown in Fig. 6is postulated by the desideratum of uncovering the conventionalcompensation drilling in master cylinders whereby any surplus liquid inthe brake system is led back to the master cylinders reservoir.Incidentally` I might state my experience that the requirement formuscular braking through the described long-stroked brake pedal did notoccur once in many months of vehicle operation on the roads with thedevice principles herein disclosed as they ail'ect such longstroked4pedal operation. Such infrequency might induce some designers toconsider full master cylinder plunger retraction as shown in Fig. 6,

' not to be absolutely required even in combination with the curentlyconventional master cylinders.

The hydraulic brake line tube |21 (Fig. 1), with the branch |28 for therear vehicle wheels, leads from the master cylinder 63 through the tube|29 to the front wheel brake, shown representatively as the Lockheedtype, comprising the hydraulic wheel cylinder |30, with its dual pistonsfor forcing apart the two brake shoes as I3I, pivoted on the adiustablyxed pins as |32, and against the tension of the shoe retract spring |33,the

The modification in Figs. 10 to 16 Fig. 10 shows an alternativestructure for part of the assembly shown in Fig. 8. Except for changeddimensions, the parts |06a, |||1a, "13a, Illa, ||I| and ||a are ofsimilar structure as the parts of similar characters in Fig. 8, exceptthat the plunger head IIlSa has a slanted groove |31 milled'thereln topermit assembly therethrough of the initially tensioned compressionspring |38, one end of which bears against the enlarged head |09a, theother end of the spring bearing against the flanged ends of the threefriction shoes, as |05a (see Fig. 9), the split cylindrical spacer |39being also inserted therebetween and encompassing the said spring |35.'I'he spring |33 functionally substitutes for the conical spring 53 ofthe vacuum motor 43 (Fig. 1) and serves the same purpose of initiatingthe lateral expansion of the rubber bar ||5a to press the friction shoesfor initial friction against the liner of the tube 50. 'Ihereuponleftward pressure on the piston member |08a, consequent to foot pressureon the brake pedal would compress the rubber bar ||6a, through thedished wlasher |40, serving to close the groove |31 against rubberentry.

The modification in Fig. 11 shows the brake actuating spring as combinedin one assembly with the vacuum motor and non-reverse lock unit, andfurthermore shows another form of expansible rubber bar principle forthe nonreverse feature. It accordingly substitutes for the disclosure inFig. 8 and for the actuating spring element oi' Fig. 1, comprising parts63 to 1|. Incidentally, it avoids the upwards thrust of force throughthe lever 59 (Fig. 1) due to the non-alignment of the rods |I| and 66,previously referred to. Aiixed to the vacuum motor 43 is the cast tube50b having the inner liner I I1, and which tube has the integral bracketextension |42 for mounting the whole unit to the vehicle chassis orframe. The vacuum motors diaphragm rod 49 has ailixed to its right endthe cylindrically symmetrical plunger head |43 having the continuousannular groove |44 accommodating a cylindrically complete set ofcombined friction shoe and tensile links as |45 (serving the samepurpose as the shoes |05 of Fig. 8), the ends of which shoes however areformed for reinforced rigidity to permit the use of thinner material.'I'he grooved conical portion |48 integral with the member |43 is firmlyvulcanized into the solid rubber bar |41 molded normally somewhatbarrel-shaped but shown of exaggeratedly restricted spool-like girth atits mid-section due to the longitudinally tensile force caused by thepull of the vacuum motor 43 in the shown position of brake release.Similarly firmly vulcanized and embedded in the right end of said rubberbar is the similarly grooved conical portion I48 of the cylindricallysymmetrical plunger head |49, having the continuous shoulder |50engaging the formed end of the friction shoes as |45, so that said shoesmay serve as pull links during the shown force-effective position of thedevice. The tube I5I, preferably cylindrically split for assemblingreasons, has its left end flanged over the shoulder of the member |49,its right end being radially outwardly flared to flange over the edge ofthe orifice of the formed savana washer head |52 which bears against thestrongly tensioned brake actuating spring |53 o! the compression type,and of laterally caged condition, so that a break in the spring wouldnot render it ineffective. 'Ihe left end of the said'spring bearsagainst the washer |54 xing the flanged end oi the spring enclosure tube|55, thus held iixed onto the bracket member |41. Cooperating with thistube 1s the additional tube |55 flanged for co-movement with the washer|52 and thus serving as a telescoping enclosure for the actuating spring|53. It is apparent that the expansion tendency of the spring |53 wouldforce the plunger member |43 and the assembly asso ciated therewithrightwards in the tube 50h upon release of the vacuum pull on the rod45, thus forcing rightwards the thrust rod |53 and consequently also thepin 55 at the lower end of the floating lever 59 (Fig. 1), for brakeapplication. Thereupon in the brakes applied position, when the brakepedal should muscularly supplement the power system for further pressurebraking, the coincidental full release of the vacuum suction in themotor 43 would cause the rubber bar |41 to contract longitudinally as ittends to return to its static barrel-shaped condition. thus exerting therequired initial pressure radially outward.: on the friction shoes as|45, for initial frictional bind against the liner I1, whereuponleftward force through the connecting rod |58, due to foot pressure onthe brake pedal would intensify the laterally expansive force in therubber bar |41 to increase the friction bind against the tube 53hl orrather against its liner ||1 in a self-locking ratio as described forFig. 8. Accordingly the inherent tension in the rubber bar |41supplantsthe conical spring 53 (Fig. l) and the spring |33 of themodication in Fig. l0. Moreover, such rubber tension would serve tobetter fill out the space within the shoes |45 upon release of thesuction in the motor 43. The tensioned tensile spring |53, mountedbetween the rod |58 and an ear welded on the washer |52, tendsconstantly to hold the rod |55 in abutment contact with the number |49,though it is obvious that other known constructions having the sameeffect may optionally be provided in lieu thereof.

The modification shown enlarged in Fig. 12 has the same relation to Fig.8, as has been described for Fig. 10. However, as shown, it employs theconical spring 53 of the vacuum motor (Fig. l) to initiate thefrictional bind, though obviously the spring principle shown in Fig. 10may replace such conical spring. It features a provision whereby theleftward movement of the plunger |||8b relative to the rubber bar I|6band to the shoes as |||6b will not tend overduly to push axially alongthe cylindrical periphery of the rubber bar ||6b, and thus reduces thetendency to force the friction shoes as |||6b with it, particularlyafter considerable wear on the frictional surfaces of the shoes as |0617or of the liner ||1, which friction shoe movement tendency the tensionstrength of the conical spring 53 or of the spring |38 were meant toobstruct, in combination with the concavity of the right end of therubber bar ||8 (Fig. 8). Moreover, the effective piston area of theplunger head |091; is reduced, and it may be made so to any optionaldegree, below the cross-sectional area of the rubber bar ||6b, as willbecome apparent. The right end portion of the rubber bar ||6b issurmounted by a series of laterally containing and continuously annularrings or bands comprising the inwardly grooved band or hoop |62, thecylindrical ring |43, the inwardly srooved band |84. the cylindricalhoop |65 and the annularly flanged and grooved cap |86, against whichlatter the piston head |881: thrustlngly abuts to compress the rubberbar ||6b upon the brake pedal muscularly supplementing the power system.The said series of rings are mutually relatively movable, and alsofreely movable relative to the friction shoes as ||l8b in the axialdirection. The juncture, for instance between the cylindrical hoop |63and its adjacent grooved ring |84 serves virtually as a rubber diaphragmelement, the rubber ||8b permitting the said ring |64 to move relativeto the hoop |63 when leftward rubber compression piessure is exerted onthe piston head |08b. It varies in a novel manner from heretoforeemployed rubber diaphragm elements, in that my disclosure will withstanda very high internal pressure in the rubber. With rubber having anelastic modulus of 1000, which is about of the order of the hardestapproximately of the commercial soft rubber stocks, of a durometerreading of about '15, 1000 lbs. per sq. inch pressure in the rubber bar||8b, would, I believe, cause the rubber to bulge out into the spacebetween the ring |63 and |64 (as per our example) to form across-section of a semi-circle. If the inner groove in the ring |84 weredesigned axially short to cause acute rubber bulging also at that point,or rather at the neck between the hoop |63 and |65, the rubber bulge atthe diaphragmatic space between the parts |63 and |64 would not be thatof a semicircle cross-sectionally. However, the suggested axialshortening of the groove in the ring |64 would cause additionaldistortion of the rubber mllitating against durability of the unit; suchdesign factors being optional according to the material employed.

Accordingly my disclosed structure is that eiectually of severaldiaphragms in series. If each of the shown four open junctures betweenthe cylindrical rings |63 and |63 with the grooved outer rings, werepermitted 1/64 diaphragmatic movement, the four would cumulativelypermit rig" piston like movement of the plunger head |0922 to compressthe rubber bar ||6b. For operation, dependence is had on the fluiditycharacteristic of soft rubber, for rubber iow from the right end of therubber bar to its main and left larger diameter portion. It is thereforepreferable to design the inner core of the rubber bar ||6b, particularlyat its right end of suitably soft rubber stock so as not to offer highstatic resistance to fluid flow of the rubber, said soft rubber corehaving optionally an elastic modulus rating of about 150 to 200.Preferably such core extends throughout the length of the rubber bar|l6b for pressure distribution. Accordingly the said soft rubber coremight extend radially up to the cylindrical hoops |63 and |65, overwhich the harder rubber rings to ll into the grooves of the rings as |64might be placed and cemented or vulcanized. It is obvious moreover, toapply the practice of placing the metal rings. |62 to |66 in the rubbermould in the usual manner of rubber to metal fabrications, which wouldinvolve rubber filling the spaces as between the member |64 and |63 butnot the spaces such as between the ring |64 and the member |62 in anappropriately made mould. Thereafter the separately formed inner core ofvery soft rubber may be inserted. The left flange of the grooved ring|62 is shown as extending radially further inwards than the anges of thegrooved ring |64. This is for the reason that the internal rubberpressure would tend to move the said ring |83 exaggeratedly to theright. which tendency the extra exposure of the larger flange of thering |42 is meant to counteract by reason of its embedment and anchoragein the rubber stock. Obviously the metal rings |42 to |88 are to be ofsuilicient strength'to withstand the maximum rubber pressure with anextra safety margin. It is furthermore apparent that the eiectual areadiaphragmatically is determined by the radius extending to the rubberflexing space between the rings |63 and |64, and therefore the area isless than that of the main cross-section of the left portion of therubber bar ||6b. If longer rubber compression rstroke is desired for theplunger head |09a, further intermediate rings., as |63 and |64, may beadded. 'I'he outer shell of harder rubber, which overlap the spacesbetween the three friction shoes as |0612, is preferably to be thin,perhaps i," thick, the dotted outlines shown in Figs. 8 to 12 beingmeant merely to indicate an outer layer of harder rubber roughly. If thevarious shown friction shoes, as |06, are preferably to be fabricated asvulcanized onto the rubber bar as ||8 by insertion of the metal shoes inthe rubber mould, such rubber may designedly be made to protrude throughthe thickness of the said metal shoes through suitable perforationspunched through the shoes, so as to provide rubber contact with theliner with the higher frictional coeicient of rubber being takenadvantage of. Buch arrangements are optional.

Fig. 13 presents another form of non-reverse lock to serve the samepurposes and in lieu of the locking devices shown in Figs. 8 to 12.Accordingiy the connecting rod 49e connects to the vacuum motor'sdiaphragm directly (see Fig. 17) without passing through a tube as 58(Fig. 1) To the pin 65 in trie noating lever 59 is pivotally connectedthe fork cievis |10, the integral extension |1.| of which connects bymeans of the pin |12 to the arm |13 of the lock member |14. Within thethroat of the fork |10 is pivoted by means of the pin |15 the connectingrod |16 having its right end slotted for lost-motion at |11 and havingits left end connected pivotally to tne pin |18 through the arm H3, towhich pin |18 is likewise connected the vacuum motors pull rod lucaiiixed to the diaphragm o1' the vacuum motor 43 (Fig. 1). Apretensioned tensile spring |19 is mounted between the lever 59 and aclip |60 aflixed to the rod |16, tending constantiy to puii the rod |16cioser to the said lever 59. The lock member |14 is axially siidablymounted on the square or rectangular steel bar |8I, held fixed by thexed brackets |82 and |83 attached to the vehicles chassis. The member|14 completely encompasses the said square bar |8|, having asubstantially square hole |84 broached therein, the right end of theupper wall and the left end of the lower wall of said hole beingsomewhat rounded with large radius for pinching grip on the upper-andlower surfaces of the bar |8| when the member |14 is tilted clockwise.The rubber dust guards |85 and |86 of the conventional-like telescopingtype are .mounted between the rod |8| and the member The parts are shownin the brakes-released position, with a heavy leftward pull on the rod49e opposing the rightward pull of the actuating spring 69 (Fig. 1) onthe rod 66, the opposing forces acting through the pin |15, and againstthe tension of the spring |19. In the shown position the lock member |14is iriotionelly free to slide on the square rod ill. eo that uponapplication of the brakes implying the release of suction pull leftwerdon the rod "c, the actuat ing spring Il will be free to pull the pin lto the right carrying 'the rods "c, |1| and |10 as also the member |14with it to the right. When however the brake pedal il is to supplementmuscularly the power system. the full release of suction pull on the rodllc will permit the tensioned spring to pull the rod |18 to the rightrelative to the rod |1|, thereby causing a clockwise tilt of the lockmember |14 relative to the square bar |8| conditioning it to bindinglyself-lock on the said bar upon forceful leftward thrust of force throughthe rod |1|, as induced by overdominanco of foot force on the brakepedal relative to the actuating spring 00. The leverage quantitiescompared with the frictional coefficient between the bar |l| and thelock member |14 are such that secure self-locking of the member |14 isattained, as seems apparent. The bar ill and the member |19 arepreferably suitably heattreated. Upon release of the foot pressure onthe brake pedal incidental to brake release, the locking effect will bebroken by the leftward pull of the vacuum motor on the rod 48e,particularly in vview of the fact that the initial foot pressure releasewill release the strain or leftward force on thc rod |1|. The pins |12and |18 may be designed apart a suitable distance to enhance the ease oflock release. The hole |84 formed in the member |14 may be grooved outlaterally to both sides of the bar |8| to provide ample passage forquick air transfer from one dust guard portion to the other. a hole inone of the two rubber dust guards taking care of any surplus airdisplacement. The spring |18 nay be mounted between the rod |16 and themember |14 close to the bar |8| to the more secure tilting of the member|14 in view oi' friction at the pins |12 and |18; in any case thetension of the said spring |19 is to be sufiicient to assure suchtilting function. It is apparent that brake pedal stroke recovery to ahigher pedal position is attainable. when it has travelled close to thefoot board |1, by mere let back of the pedal, permitting the spring 69to pull the member |14 farther to the right.

Fig. 14 shows a modified leverage changing system though incorporatingthe same fundamen tais as shown in Figs. 3 to 7, which the structure ofFig. 14 replaces. It provides a greater freedom for quantitativedesigning for adaptation to some vehicles in which existing chassisobstructions might be encountered. It presents some further variationsin details; also an electric bulb indicator giving notice to the driverthat the brake pedal is seeking its long-stroked position, as will laterbecome apparent. The brake pedal |5d has the integral arm |81 carryingthe pin |88 pivoting the double forked toggle link 82d resting normallyagainst the stop |89 on the arm |81, to which link is pivoted by the pin8|d the thrust rod 15d pivoted to the upper extremity of the floatinglever 99d by means of the pin 14. Connected to the pin 65 of the lever59a', is the actuating thrust rod |58 of the power unit shown in Fig.11. The master cylinder plunger 6| is pivoted by the pin 60 to the lever59d and to the stamped channel-like lever i 9| fulcrumed by means of thepin |92 on the fixed bracket |93 having the integral stop arm |94against which the lever |9| rests when the brakes are released. Thethrust link |98 is pivotally connected by the pin 58d to the lever 59dat its right end, while its left extremity is formed as an aaneen openslot |00 to engage the large headed stud pin |80 amxed to the lower arm18d integral with the brake pedal, and which arm is suitably oifset topermit freedom of toggle collapse of the links 10d and 82d. The rod |08is also offset when required by the quantitative designing to preventinterference with the down-swing of the link 82d. The retract spring|2411 of closed coils and with initially stored tension is mountedbetween the lever Bld .and the nxed ear |28d with lost-motion extensionof the spring's end |20d to function and to serve the described purposesof the spring |28 of Fig. l. The rod 10d has formed therein the springwell 20| accommodating the tensioned compression spring 202 bearingagainst the upper wall of the well and against the plunger head 208integral with the stem 204 passing through a drilling in the upper wallof the well and threaded to receive the adjusting nuts as 208 abuttingexternally against the upper wall of the spring well. the wholepresenting a well-known tensioned spring assembly. The plunger head 208is adapted to contact onto the shelf bracket 200 integral with the lever58d, the adjustment of the nuts as 205 permitting pressure of the head203 against the said bracket 208 suilicient to secure contact betweenthe link 82d with its stop |89 in the shown full leftward position ofthe power rod |58, namely that of full brake release. shown in Fig. 15is meant to be connected to the brake pedal lod at a suitable point onits upper arm above the bearing pin I8. As will appear from thedescription of the device in Fig. l5, the valve connection tends toreturn the pedal lid with fair accuracy to its proper normalbrakesreleased position, namely that of the food pad Il to the positionshown in Fig. l. This permits prevention of a surplus pedal bounce-backupon brake release, a factor previously referred to.

The operation of the device in Fig. 14 is mostly understandable from thedescription applying to Figs. l to 7 and Fig. 11. Instead of the pedalslower arm 13d directly contacting the pin 68d, it acts thereon throughthe link |96. As to the brake pedal |5d retracting abnormally to itslongstroked position, as may be due to a leak in the vacuum motor orvalve: Said gradual vacuum leak would cause the pin 85 to move graduallyto the right, whereupon, after the lost-motion and after the mastercylinders compensating drilling covering by slight rlghtward movement ofthe master cylinder plunger 6i, particularly after the lost-motionbetween |23d and |25d has been negotiated, all as previously explained,the pin il is forcefully moved leftwards thus revolving the pedal |5dclockwise on its fulcrum pin I6 for abnormal retraction. After the pin|88 has rocked with the pedal sufficiently upwards the toggleautomatically collapses by downward movement of the pin Bld, with theresult that the link |96 will rest and press on the bearing pin |99 forfurther and ultimate retraction of the brake pedal. Sulcient upwardmovement of the said pin |88 for secure collapse of the toggle can beassured by designedly having the pedal |5d retract a suiiicient amount,so that the foot pad i8 assumes a position even rearward of theconventional long stroked pedals of current use, the leg convenience notbeing a. weighty consideration because of the infrequency of theoccurrence. Thereupon muscular application of the brakes is had throughthe connection through the link |96. Upon re-availability of the vacuumwhen the pedal |5d is inits abnormal long-stroked position,the pin 65willbe pulled to the left to its The valve shown position in Fig. i4,during which operation the toggle linkagev will tend tostraighten out.its final straightening being aided by the.

spring 202. Moreover. as an assistance, the valve of Fig. l5 will tendto prevent the pedal Ild from depressing below the normal position o!the loot pad I as shown in Fig. 1. This effect o! the valve in Fig. 15cooperating with the spring |53 will assurethe shown checking contactbetween the radius lever 19| with its stop |94. An analysis of theforces would disclose that the spring 202 would aid in assuring contactbetween parts |91 and |94. It is optional to provide an elongated closedslot for lost-motion in the bearing o! the link 82d over the pin |33,similar to the lost-motion slot 33 of Fig. 3, except that the slotshould be closed to prevent disassembly of the link 02d from the pin|33. With such provision quantitative designing would provide thatdirect contact between the link |93 and the pin |99 would take care ofthe nal supplemental braking through the movement of the foot pad from[3c to |8d (Fig. 1).

In Fig. 14 is furthermore disclosed an indicator in the form of a lightbulb located preferably on the vehicles instrument panel to give noticeto the driver that the brake pedal is assuming its abnormal long-strokedposition. It is particularly useful in combination with a form ofaccelerator disconnecting devices which do not ailect acceleratordisconnection automatically upon such abnormal retraction of the brakepedal, and as is disclosed in my application No. 399,908. Alxed beneaththe foot board l1 is the fibre block 208 on which is mounted theconducting blade spring 209 bent so as to be in the path of the stud 2|0ailixed to and laterally projecting from the brake pedal |d upon thepedals abnormal retraction to its long stroke position. The conductingwire 2li electrically connected with the said blade spring leads to oneterminal of the electric light bulb 2|2, preferably of the on-and-oiilasher type as employed commonly for motor vehicle stop lights. Theconductor 2|3 leads from the other terminal of the bulb to the switch2|4, representing the ignition switch of the vehicle. Thence theconductor 2|5 leads to the battery 2I6, the conductor 2|`| thenceleading to the ground. shown as connected electrically to the brakepsdals bearing pin i6. After the ignition switch 2 i4 is closed,retraction movement of the brake pedal will carry the stud 2 l0 upwardsfor electrical wiping contact with the blade spring 209 thus closthecircuit through the battery 2|6 and the light bulb 2|2, illuminating thebulb, of any suitable color as red, to indicate to the driver that thebrake pedal rests no longer at its normal low position. The bulb 2 2 isrepresentative of any suitable form of indicator.

Figs. 15 and 16 show a combination oi' vacuum controland check-valve forconnecting to the upper arm of the brake pedal (see Fig. 17), assubstitute for the valve 42 with its connections inclusive of the rod 95(Fig. 1), and furthermore substitutes for the cushion spring 16 (Fig.4), so that the parts 15 and 13 (Fig. 4) may be constructed of onepiece. It serves the purpose of providing an optionally long valveoperation stroke relative to the stroke of the brake pedal, and ispressure-indicated in the sense that it con.. trols the vacuum valvingaccording to the desired vacuum pressure in the vacuum motor 43. Thecheck-valve portion has particular characteristics tending towardleak-proofness.

The ilxed valve body 22| has symmetrically cylindrical axial borestherein of various diameters. a large bore establishing the exhaustchamber 222 (I speak of vacuum conveniently, as though it were apositive pressure) enclosed by the cap 220 retaining the cylindricallysymmetrical metal partltion 224 having multiple pei'iorations as 220leading into the iilter material 223 cylindrically surrounding thepartition, air inlet drillings as 221 being provided in the cap 223 topermit atmospheric air to course through the illter into the chamber222. Integral with the cap 223 is the drilled guide cylinder 229accommodating for axial sliding the lower end 230 of the valve stemcomprising the cupped valve seating member 23|. A tensioned compressionspring 232 tends constantly to urge the valve member 23| rightward forvalve closing pressure along its periphery on the annularly symmetricaldiaphragm rubber 233, the inner lip of which fits snugly and may becemented within the corresponding recess formed in the inner diameter ofthe cylindrical valve thimble 236, axially slldable in the smallestdlametered bore of the valve body 22|, and provided wlth severalradially extending nils as 236 to permit axial air passage and to guidethe axial sliding movement of the thimble in the said bore.

The thimble 235 has integrally the ange 233 adapted to checkinglycontact and rest upon the adjacent shoulder formed in the valve bodywhen the said thimble is in its rlghtmost axial posi.. tion. The saidthimble 235 is furthermore grooved away at its lower periphery so as topermit diaphragmatic ilexing of the valve rubber 233, which rubber isheld in the assembly by the ilared upper end of the partition 234. Theaforesaid smallest diametered bore of the valve body is annularlyenlarged at its middle portion forming the continuously annularsegmental boring 0 249 for enlarged air passage into the bore from Theother ground conductor 2|9 is l the chamber 24| of the check-valveportion to be later described. The right end of the afore said thimble235 has the integral continuously annularvflange 242 of an outerdiameter to en able it to pass through the aforesaid smallest bore ofthe valve body during assembly, under the peripheral edge of which angeis inserted the annular rubber seat washer 243 slightly overlapping theedge of the said small bore so that the said flange 242 may shearinglyseat on said rubber washer for valve closure as is shown. rhe rubberwasher or gasket 243 is surmounted by a thin metal washer to retain itin assembly, onto which metal washer bears the tensioned compressionspring 245, the spring bearing at its right and movable end against themetal guide Washer 246 surmounting the valve stem 241, which Washer 246itself bears rightward against the cupped metal diaphragm reinforcingplate 248 supporting the rubber diaphragm 249 held sealingly on thevalve body by means of the cap 250 having the air passage drilling 25|therein and domed to accommodate the sphere 252 of the ball-jointelement, which sphere is integral with the operating thrust rod 253. Theright extremity of the valve stem 241 is shouldered to serve as rest forthe metal washer 255, and is furthermore threaded to receive the ballsocketing nut 25B, which clamps the inner periphery of the rubberdiaphragm 249 is assembly against the washer 255, which latter ishermetically sealed, during assembly, at its juncture with the stem 241to obviate leaking. In the shown position the washer 255 forcefullybears against the cupped plate 248. It is apparent that there are twoannular locations of diaphragmatic action ot the rubber 243, the largerdiametered at 253 and the smaller diametered at 25|. The rubberdiaphragm is to rest on the surface 280 when in its rightmost positionand rests on the shoulder 23| or the valve body, when in its leftmostposition. The compression spring 282 oi stored tension bears on thevalve thimble 238 and against the washer 248 and serves the purpose ofurging the valve thimble 235 constantly leftwards for valve seatingpressure against the rubber gasket-243. The spring 232 however securelydominates the tension in the spring 282.

The operating rod 253 extends rightward into the restricted guiding tube281 for axial slidability therein, and during operation abuts againstthe axially slidable spring plug 238 adapted to be checked by theshoulder 283 formed in the spring enclosure casing 210 containing thetensioned compression spring 21| bearing at its left end against thesaid plug 288 and at its right end against the right wall of the springenclosure tube 210 plvotally connected by means of the pin 213 to thebrake pedal |d or |5e (Fig. 17) which represents the upper arm of thebrake pedal, as l5, the pin 213 being located a suitable distanceupwards from the pedal's bearing pin I8. The tube 214 in freecommunication with the chamber 265 leads to the vacuum motor 43 (Fig.l).

As to the check-valve structure, shown particularly in Fig.- 16, thetube 40 leads to the engines intake manifold 35 (Fig. 1), and is in freecommunication with the chamber 211 and by reason of the centralperforation 218 in the rubber diaphragm member 219 is also in constantcommunication with the chamber 288 above the said diaphragm. The discportion of the said rubber diaphragm is preferably reinforced by a metalplate embedded therein during its manufacture, as is shown in Fig. 16.The customary conical spring 28| lightly urges the diaphragm downwardsto seat normally on the continuously annular and upstanding rim 282 forclosing communication between the chamber 211 and the continuouslyannular chamber 24| in constant communication with the annular bore 240Within the valve body 22|. The cap 283 held onto the valve body byscrews or any suitable means sealingly ietains the rubber diaphragm 219in assembly and prevents atmospheric entry into the chambers, asconventionally with diaphragms.

As to the operation of the check-valve shown in Fig. 16: The valve isshown seated. Should tne intake manifold suction existing in the tube48, and chambers 211 and 280 exceed the suction pressure existing in thechamber 24|, in communication with the control valve of Fig. 15, thesurit is apparent that perfect sealing can he attained on the smallercircumferential rim area of the seating rim 282. Furthermore such largeexposed area has relation to the tension of the spring 28|, thusreducing the pressure differential incurred by such valve springs, oralternaasvasea tively permitting a more strongly tensioned spring forinitial seating` purposes. The feature of providing the communicationhole 213 in the center of the diaphragm permita structure simplicity.'Ihe size of said hole 213 can be designed to obviate valve iluttering.The rubber at the seating rim may be soit for better sealing.particularly on a somewhat fiat seating rim.

As to the operation oi the vacuum control valve of Fig. 16: The parteare shown in the brakes-applied position, with the brake pedal Ild helddepressed by the footl and immobile so that all valve ports are closed.However. as shown. the brakes are not applied with an overheavy brakingpressure to tax the capacity ot the power system, therefore vacuumauction exists in the valve which suction acts' on the ieit side oi' thelarger diametered rubber diaphragm 243, which is exposed to the vacuumsuction existing in the vacuum motor 43. This type of compensating valveis one of balances between the various spring and suction forces. Shouldthe brake pedal Ild be depressed leftwards still farther than is showncorrespondingly extra tension would be given to the spring 21|, thusdisturbing the balance causing the valve stem 241 to move leitwards,with the consequent unseating of the valve member 23| oi! oi' the rubber233, the valve thimble 235 being held virtually unmovable by reason ofthe seating of its ilange 242 on the rubber gasket 243. Said unseatingof the valve member 23| permits'atmospheric air to enter through thefilter 228, past the valve member 23| and through the axial hollow ofthe thimble 235 into the chambers 284 and 285 and consequently into thevacuum motor 43 in free communication with the said chambers. Theresultant reduction ot vacuum suction in the chambers 284 and 285permits the diaphragm 248 to move compensatingly to the right as urgedchiefly by the spring 245 and auxiliary by the springs 282 and 232,which rightward diaphragm movement carries the valve stem 241 with it byreason of the contact of the cupped plate 248 against the washer 255,thereby again closing the valve by seating the valve member 23| againstthe rubber 233. Such action accordingly is determined by the suction ofthe vacuum pressure in the chambers 284 and 285 and in the vacuum motor43, the whole eil'ect being initially determined by the tension in thespring 21| which tension depends upon the amount of foot depression ofthe brake pedal |5d. On the other hand, should the brake pedal |5d bepermitted to retract slightly for the purpose of decreased brakingpressure, the tension in the spring 21| would become decreased, with theresult that the springs, such as 245 would force the whole assemblyincluding the valve stem 241 to the right, which implies that the valvemember 23| pressing on the rubber 233 which rests on the thimble orsleeve 235, would consequently force the said thimble 235 also to theright against the tension of the small spring 282, thus causing the ange242 to become unseated from the rubber 243, consequently permitting thesuperior suction in the engines intake manifold (Fig. 1) to draw airfrom the chambers 254 and 285 and from the vacuum motor 43. This airwould pass from the vacuum motor and said chambers through the valveopening at the flange 242, past the guiding nibs as 238 into the bore248, thence into the chamber 24| and into the chamber 211 (Fig. 16),because with the superior intake pressure the check-valve `would beopened, thence through the tube 40 into the engine's intake manifold 35.Such air suction from.

the vacuum motor 43 would increase the suction pull on the motorsdiaphragm and thus reduce the braking pressure. Such increased suctionin the vacuum motor and in the chambers 264 and 265 would act to forcethe rubber diaphragm 245 leftwards, thus permitting the then instanttension in the spring 21| to move the assembly including the valve stem241 and the thimble 235 leftwards to again close the valve by seatingthe flange 242 onto the rubber 243. Thus again the tension in the spring21| determines the vacuum suction in the vacuum motor 43.

As to the operation of the valve in Fig. 15, for full brake release:Removing foot pressure fully from the brake pedal I5d will permit thespring 21| to expand until the spring plug 268 rests upon the checkingshoulder 269. Simultarheously the valve stem 2,41 and the valve thimble235 will move to the right thus unseating the flange 242 from the rubbergasket 243 to introduce increased vacuum suction in the motor 43 toretract the brake system. The thimble 235 can move to its rightmostposition, in which position the flange 238 integral with the thimblewill rest on the shoulder of the valve body, the spring 232 beingtensioned suiilciently not only to eect leakless seating on the rubber232, but also having surplus tension, if so desired, to aid insupporting the weight of the brake pedal |5d which latter is optionaland depends upon other optional factors in the complete design. It ismeant, though not accurately shown in the drawing of Fig. 15, that therubber diaphragm 249 rests on its stopping surface 260 on the cap 250 soas not to apply the pressure of the spring 245 against the washer 255when the lian-ge 238 0f the thimble 235 rests on its adjacent checkingshoulder of the valve body, therefore not exerting undue pressurebetween the valve member 23| and its rubber seating diaphragm 233. whichrubber may optionally be made fairly soft for normal valve operationpurposes. To accomplish such desired earlier seating of the rubber 249on the cap rest 260 the stroke distance between the flange 238 of thethimble and the stop shoulder in the valve body against which it restsshould be made longer than the stroke of the rubber 249 to its coactingseat. The area of the vacuum motors diaphragm in relation to theactuating spring 69 (Fig. 1) might, for example, be designed so thatabout I2 inches of vacuum suction in the motor will fully release thebrakes against the tension of said actuating spring. The combinedtensions of the valve spring 245 and 262 would be designed to reouiremore than such 12 inches of vacuum suction, well say 13 inches, to drawthe rubber diaphragm 249 awav from its resting position against thevalve cap 258. Surplus initial tensioning to compensate for such l inchdifferential pressure may be provided in the spring 21|, if desired. Onthe other hand it is not objectionable that the combined tensions ofsaid springs as 245 be less than the moment equivalent of 12 inch vacuumsuction requirement to operate the diaphragm 249: in such case howeverthere would be no proper valving for the very initial pressure braking.as might be desired for icy roads. Furthermore, since gasoline enginesin good condition supply about a maximum of 20 inches of vacuum suction.it is apparent that, when the brakes are in release during such suctionconditions, the diaphragm 249 would be drawn to the left until itssupporting plate 248 rests on the rim 26| of the valve body. Whenthereupon applying the brakes through pedal depression, the very initialvalve operation would instantly eliminate the surplus suction in thevacuum motor, permitting the diaphragm 249 to move promptly rightwardfor control contact with the washer 255. It is apparent that thediaphragmatic action of the rubber 249 for its diaphragmatic radius tothe point 259 permits the diaphragm 249 to rest leftward on the rim 26|,as aforesaid, while permitting the stem 241 with its attached parts toremain in its rightmost position for retaining the valve closed. 'Ihepurpose of providing a stop shoulder 238 on the thimble 235 is to permitthe full surplus force oi the spring 232 to press for valve closingbetween the valve disc member 23| and the rubber 233 for betterleaklessness, whereas during the actual valve operation, and in theposition shown, the tension of the spring 262 determines the valvingpressure or seal at the valve seats. The said ilange 238 is accordinglyoptional. The choice of tension variation of the spring 21| per strokeobviously determines the normal valving stroke of the pedals foot padI8. For example, if the pivot pin 213 is located halfway down from thepedal pad I8 in respect to the pedals fulcrum pin i6, and if designedlya total of 1 inch pedal depression stroke at the foot pad I8 is desiredfor the whole power control of valving operation, the spring 21| shouldbe designed for a tension variation so that l/2 inch of its compressionincreases its tension to an extent to fully carry the load of thesprings as 245, because at that stage of the pedals depression it isdesired to reach zero vacuum suction in the vacuum motor 43 thuseliminating any suction aid to hold the diaphragm 249 leftward to itsshown operative position. Upon still further pedal depression beyondsuch assumed 1 inch stroke, the range of muscularly supplementing thepower system will begin, involving that the valve stem 241 and the valvemember 23| will move still farther leftward than is shown in Fig. l5until the plate 248 rests on the rim 26| to determine the limit of theleftward movement of the valve stem 241, during which conditionnaturally the member 23| will be raised ofi of the rubber 233 holdingthe valve open. The extra length of the spring 21| will permit the footpad I8 to reach all the way to the foot board |1 during such muscularsupplementing of the power. Said extra compression of the spring 21|will exert an eXtra load on the foot, which however is not meant to beimpractical, since the total foot work for normal valve operation is tobe suitably light. On the other hand provisions are known to minimizesuch extra foot load by providing an additional spring in series withthe spring 21|, such extra spring being checked against a shoulder as269 for the spring 21| for suitably heavy initial tensioning and havinga long stroke per tension variation. The amount of initial tensioning ofthe spring 21|, namely its stored tension when the spring head 268 restsupon the shoulder 269, is optional. It may be designed suilicient sothat the spring 21| does not compress during the initial valveoperation; or it may be designed for slight compression initially tomeet the load of valve operation, thus making the pedal less sensitivefor such initial operation, in other words permitting a cushioningdepression before operation of the valve. The said amount of initialtension of the spring 21| is attained by the location of the checkshoulder 269. For convenient reasons I have omitted threaded adjustmentsin the drawings for spring tensions and for connecting rod lengths. Thelength of the guide tube 281 in which the rod 253 ahlally 'slides shouldbe sumcient to permit the brake pedal to assume its abnormal long strokeposition.

Some special features, otherwise perhaps overlooked, in the valvestructure of Fig. 15 might be noted. The braking pressure modulationmovement of the thimble 235 is very small, since the valving at therubber 233 occurs almost instantly after the thimble 235 has beenbrought to rest on the rubber 243, thus almost simultaneously openingone valve after the closure of the other upon a continued movement ofthe valve stem 241. It so operates also reversely. To enhance valveresponsiveness still further I provide that the vacuum suction existinginside of the valve does not substantially Vaii'ect in its fluctuationsthe moving valve members, except for the intended eiiect of the suctionon the rubber diaphragm 249. For this reason. the effectual area of thediaphragm radiused to its nexing portion at 259 approximately equals thearea of the valve member 23| for mutual equalization, thusremovingsuction pressure influence on the valve stem 241. Moreover, theeffectual diaphragmatic area of the rubber 233, radiused to its flexingcircle approximately equals the crosssectional area of the small bore inthe valve body 22|, in other words about equals the area of the valvecircle at the rubber 243, and also approximately equals the area of thevalve member 23| for its seating on the rubber 233 and therefore almostcompletely eliminates influence of suction either in the main chamber265 or in the chamber 240 from having axial force effect on the thimble235. Furthermore, the vacuum pressure differential existing between thechambers 248 and 265 is equalized to all lateral portions of thethimble, thus removing resistant friction (also consequent wear) betweenthe thimble 235 and the valve body during the valve operation, suchsuction pressure diilerential being large upon full valve opening,namely when the suction in the chamber 265 is reduced to zero. Moreover,the valving oriilces are linearly long extending for the full peripheryof the valve member 23| and of the ilange 242, thus permitting copiousflow per valve movement, while at the same time providing sensitivechecking of undue ilow by reason oi' the prompt responsiveness of thediaphragm action of the rubber 249 enhanced by the diierential dynamicpressure of flow between the main chamber as 285 and the vacuum motor,with the time elapse required. to equalize the pressure at static. Suchfactors of valving responsiveness count for reduced foot work with equalbraking pressure modulation; or inversely, for better braking pressuremodulation with equal foot work. The three springs inside of the valvebody 22| have a short operative range, and if designed for a maximumstress safely below the elastic limit with proper margin, would endureindeiinitely, except for possible corrosion, in view of the number ofoperations during the life of the valve.

If it be preferred not to load the spring 232 with the extra load of theweight of the brake pedal, an additional spring assembly identical tothe parts 253 rightward to the pin 213 may be pivoted to the brakepedal, just as is pin 213, with the left end o! the rod 253, however,pivoted on a fixed pin. The tension of the spring, supplanting thespring 21|, should then'be lighter than that of 21|.

Supplemental explanations It should be observed that the leverage ischanged also advantageously for the power actuation, in the sense thatcontact between the lower pedal arm 13 (Fig. 1) with the pin 58 duringthe brake pedals power-supplemental over-depression when the pedal padI8 reaches the point llc, would switch the fulcrum for the springactuation of the lever 58 from the pin 14 to the pin 58, establishing,for example, double the leverage advantage for the actuating spring 43for braking eiect. Such transition would lbe gradual with the switch ofload from the pin 14 to the pin 58 while both are in contact, and as isregistered in a corresponding gradual resistance to the foot and istherefore practically controllable because of such increase in footresistance. Should the power system, comprising the vacuum motor and thespring 89 be designed of a capacity to take care of thefull range of allnormal pressure` braking, the non-reverse lock means shown in Figs. 8 t013, may optionally be dispensed with, since said fulcrum switching atpoint llc might be considered satisfactory for taking care of theexceptional conditions when heavier than such normal braking pressure berequired, as might be dependent upon the condition of the brake linings.It should be remembered that contact of the arm 13'and the pin 58 whenthe pedal pad has depressed down to the point |8c is meant to occurpreferably when the brake linings are worn to an extent to advisereadjustment of the brakes. Accordingly with less lining wear saidcontact and fulcrum switching would occur before the pad I8 reaches thepoint |8c. The substitute lever system shown in Fig. 14 affords agreater margin for such quantitative designing, particularly withcertain existing chassis structures of some vehicles. Incidentally, asis shown in Fig. 3, some initial lost-motion is preferably providedbetween the pedals arm 13 and the pin 58, when the brakes are inrelease. This lost-motion permits valving initiation without asimultaneous heavier load on the foot. lf however it be desired toprovide a sturdier resistance for the pad i8 initially, the arm 13 maybe designed to contact the pin 58 for the shown full brake releaseposition shown in Figs. l and 3.

It should furthermore be observed that the foot force leverage throughthe pin 14 under the condition that the foot muscularly supplements thepower system with the non-reverse lock devices such as Fig. 8 eEective,is of such quantity, particularly if the pedal designedly has lightresistance for light foot Ipressure for normal braking, that thehydraulic brake system can readily be abused with heavy over-pressure,should the foot for any incidental reasons press over-heavily on thefoot pad I8. To prevent such abuse, the overload-relief device for thehydraulic brake system, as disclosed in my application numbered 404,688may be provided. It is apparent, however, that such extra provisionwould not be required. if the lock devices shown in Figs. 8 to 13 wereomitted, as assumed in the preceding paragraph above, provided that thecapacity of the power system when operating on the pin 58 as a. fulcrumis not sufilciently large to involve such abuse to the hydraulic brakesystem. Moreover, it is optional, of course, to provide strongerstructure for the hydraulic brake system. And the assump-

